Field of the Invention
The present invention relates to a light source unit including a luminescent material plate and a projector including the same light source unit.
Description of the Related Art
In these days, data projectors are used on many occasions as an image projection system which projects an image of a screen and a video image of a personal computer, as well as images based on image data which is stored on a memory card or the like on to a screen. In these data projectors, light emitted from a light source is collected to a micromirror display device called a DMD (Digital micromirror Device) or a liquid crystal panel for displaying a color image on the screen.
Conventionally, the mainstream of these data projectors has been those which utilize a high-intensity discharge lamp as a light source. In recent years, however, there have been developed and proposed, many projectors which utilize, as light sources, red, green and blue light emitting devices or laser diodes or solid-state light emitting elements such as organic ELs or luminescent materials.
It is easy to miniaturize a light source unit which utilizes laser diodes, and the light source unit utilizing the laser diodes can be formed into a small, high-intensity light source unit which is suitable for the projectors described above. However, speckle noise is generated in a projected image using laser beams, resulting in a reduction in image quality of the projected image from time to time.
The Japanese unexamined patent publication No. 2012-185980 (JP-A-2012-185980) proposes a light source unit which emits red light, green light and blue light by the use of a wavelength conversion element which utilizes a luminescent material and a laser beam as excitation light, and luminescent material plates have also been provided which enable the formation of a small, high-intensity light source.
Further, in order to provide a high-intensity and long-life light source, it has also been practiced to translate into parallel a luminescent material plate which functions as a wavelength conversion element in such a way as to vibrate it to thereby change a shining position of excitation light on to the wavelength conversion element, so that the deterioration or burning of the luminescent material can be prevented.
Light sources like the one described above in which the laser beam is used as excitation light and the luminescent material plate which functions as the wavelength conversion element is vibrated are suitable for use in an image projection device such as a projector as small, high-intensity and long-life light sources. However, in light sources in which a laser beam is shone on to a translating luminescent material plate, flicker occurs locally on a screen, making it difficult for an image to be visualized.